This invention concerns a magnetic recording medium used for magnetic recording and reproduction devices, particularly audio and video record/playback devices.
In order to improve the anti-abrasion and lubrication properties of a magnetic coating film on the magnetic recording medium used for conventional magnetic recording and reproduction devices, a lubricant, such as ester of fatty acid or fatty acid amide, and abrasive grains of a higher Moh's hardness are conventionally added to the magnetic layers. This method can considerably improve the anti-abrasion properties of the magnetic coating film but abrasive grains accelerate wear and tear of a magnetic head often to an unacceptable level. Further, even if a lubricant is added, the lubricating effect will be lost due to evaporation or dissipation as time elapses. It is necessary to design a method to gradually transfer the lubricant into the magnetic coating layer in order to overcome such problems; however, it is extremely difficult to control the amount of transferring lubricant. The desired lubrication effect is, moreover, easily adversely affected by the environment, particularly by moisture.
In the past, methods have been proposed for improving the anti-abrasion and lubricant properties of the magnetic coating film on the magnetic recording medium. Examples of such methods are described in one or more of the following Japanese Laid-Open patent applications (JPA): 57-162127 entitled "A method for making abrasive particles of 6 or higher Moh's hardness and needle-like iron oxide coexist"; JPA Laid-Open No. 57-150131 for "A method of adding to a magnetic layer carbon black of 30 .mu.m average particle diameter and needle-like non-magnetic powder"; JPA Laid-Open No. 57-162128 for "A method of using abrasive of 6 or higher Moh's hardness, colloidal SiO.sub.2, fatty acid, and esters of fatty acid together"; and JPA Laid-Open No. 57-123527 for "A method of using polyethylene wax and molybdenum disulfide or powder of flurorine containing resin together". Despite these numerous and detailed suggestions in the art, such proposals have not quite satisfactorily improved the anti-abrasion and lubrication properties of a magnetic coated layer.
An object of the present invention is to provide a magnetic recording medium which has superior anti-abrasion and lubricant properties in the magnetic coated layer, the lubrication of which lasts and is effective for a long period of time, excellent properties which are not easily affected by environmental changes, the magnetic head which is contacted by the magnetic recording medium is not easily worn, and which has less jitter (jitters cause phase shift of the pulses resulting in blurring of the screen image) and less sliding noise as the medium traverses the recording head and other mechanical tape-handling components of the record/playback device.